Process of preparing an improved injection engine fuel



Dec. 19, 1944.

'r. H. SCHULTZ ET AL 2,365,220

PROCESS OF PREPARING IMPROVED INJECTION ENGINE FUELS POROUS PLATE----- Filed July 10, 1939 WATER 24 GAS SEPARATOR TREATER ,25

AIR ACCUMULATOR.

AIR

WATER FEED TANK 1 AGITATOR STORAGE INVENT-ORS .THOMAS,. H. SCHULTZ IRVING E. LEVINE HOMER B. WELLNIAN ATTORNEY Patented Dec. 19, 1944 PROCESS OF PREPARING AN INJECTION ENGINE FUEL Thomas H. Schultz, Richmond, and Irving E. Levine and Homer B. Wellman, Berkeley, Calif, asslgnors to Standard Oil Company of Callo, Callf., a corporation of fornla, San Francisc Delaware Application July 10, 1939, Serial No. 283,636

' 18 Claims. (Cl. 196-142) This invention relates to fuels for internal combustion engines of the Diesel type. in which a liquid fuel is injected into a combustion chamber and ignited by compression, and it has particularly to do with the modification of ordinary hydrocarbon fuels of the Diesel and more volatile than Diesel types in such a manner as to enhance their combustion characteristics for Diesel motor purposes.

In the attainment of minimum engine knocking, the time interval between the instant of liquid fuel injection and the instant of ignition, referred to as the "delay period, should be as brief as possible. Generally, this delay period is known to be affected by the type or character of the hydrocarbons composing the fuel; also,

it may be shortened by the addition to the fuel of various more or less pure chemical accelerators or primers, and certain organic nitrates, nitrites and peroxides are known to be effective for this purpose. Such ignition accelerators orprimers are mechanically admixed with or dissolved in the fuel hydrocarbons, generally in amounts between 0.1% and -10% by weight of the fuel hydrocarbons. Thesesubstances are often costly and sometimes hazardous to prepare and handle; their uniform and permanent incorporation in the fuel is occasionally uncertain and, in some cases, the beneficial ignition effects are attended by adverse effects of other sorts.

In the present invention, fuels of high igni tion quality, as measured'by decrease in delay period and by ease of cold motor starting, are prepared by derivation from the petroleum hydrocarbons which themselves compose the usual higher than about 5 and preferably of higher than 50 or 100; treating the said selected or preliminarily prepared set of hydrocarbons with air, oxygen or an oxygen-carrying gas under such conditions as will allow it to attain an oxygen factor of 5 or more, generally without concomitant increase in neutralization number of more than about 15 and often of not more than about 8 or 10; arresting the said oxidizing treatment before the oxygen factor of the oil has decreased to below about 5; and removing acidic oxidation products that have been ascertained to be detrimental for the purposes of the invention. This partially oxidized oil may be employed as an injection engine fuel, in and of itself, or it may be blended with one or more ordinary hydrocarbon fractions of the same or difupon the oxygen factors obtained; for example,

whole Diesel fuels or may be slightly more vola tile than the usual whole Diesel fuel, or fractions thereof. This derivation, in its simplest terms, is through a carefully controlled partial oxidation of a kerosene distillate or Diesel fuel hydrocarbon distillate or portion thereof, under definitely ascertained circumstances followed by a supplementary treatment designed-to stabilize the composition which is produced and to free it from components adverse in their effects upon Diesel engine operation, upon'deterioration in storage, upon physical'homogeneity and the like. As prepared, the fuels of the invention are low in cost, of consistently high'ignition quality, sufliciently permanent and stable in storage, and generally without adverse qualities from the standpoint of marketability.-

In their barest outline, the processes of the invention-provide for the preliminary selection or treatment of a petroleum fuel of kerosene distillate or ordinaryDiesel fuel distillate characteristics, or a portion of such a fuel, by such an oil of high oxygen factor may contain 2.0% or more of chemically combined oxygen.

The processes and the compositions of the invention may best be described by reference to a number of specific examples.

Example I.A Midway (California) crude gas oil distillate fraction having the following characteristics:

was treated at ordinary temperature with 1.0 pound of 98% H2804 per gallon. The sludge was settled and removed and the treated oil was washed with water, neutralized with caustic soda solution and again washed with Water to remove acidic products and soaps of sulfonic acids, in the usual manner. The treating yield was 93 volume per cent, and the treated gas oil then had the following characteristics: I

Gravity API 30.3 Pour point -4 F. Below Viscosity, SSU at 100 F 38.2 Cetane N 36.5 U. 0. P. characterization factor"; 11.32

Cold engine starting temperature F 62.5

This preliminary treated oil was heated to 290- 300 F. and transferred to a vertical cylindrical vessel or "still ofchrome-nickel steel equipped with a horizontal porous plate partition near the bottom (Filtros plates grade R, manufactured by Filtros Inc East Rochester, New York) and provided with heating or cooling coils and with a vapor condenser. A concentrated solution of calcium naphthenate in oil was added, in an amount such that the final proportion of the salt was 1.0% by weight; also 2% by volume of "seed stock" (completely prepared fuel of the invention, from an earlier preparation) was added.

The oil was maintained at 290-300 F. and air, finely dispersed by passage through the interstices of the porous plate partitions, was passed therethrough for 1% hours at the rate of 2 volumes of air per minute per volume of oil. During the first part of the reaction heat was supplied through the coils, to compensate for the cooling caused by evaporation; during the latter part of the reaction less heat was needed and cooling is indeed sometimes required, as the reaction is exothermic; in any case, such oil as evaporated was liquefied in a stainless steel condenser, condensed water was trapped out, and the condensed oil was returned directly to the main reaction mixture. After 1% hours of blowing under these conditions, the oil had an oxygen factor of 425, a neutralization number of 4.9 and a saponiflcation number of 19.3. The blown oil was then cooled rapidly to 100 F. by passage through a heat exchanger, air passage being continued in the main vessel until it was .empty oil.

The blown oil was washed at atmospheric temperature with water, in which the calcium salts or soaps of moderately strong organic acids became suspended or dissolved and were hence removed from the oil. Such organic acids as were present in the oil were then removed by scrubbing with 5% caustic soda solution, added in an amount not over in excess of that required. Finally, the oil was washed with water and brightened in a rock brightener in the usual asoaaao The temperature of the charge was maintained at 290-300 F. and air, finely dispersed by the porous plate partition, was blown through it for 1% hours at two volumes air per minute per volume of oil. The blown oil was then rapidly cooled to 100 F. by passage through a. heat exchanger, continuing the air passage in the reaction vessel until the same was empty of oil. This,oil had, at this stage, an oxygen factor of 522, a neutralization number of 5.9 and a saponification number of 20.0.

The oil was washed with water to remove calcium salts of organic acids (by partial solution and suspension in the water) and free acids were then removed by scrubbing with 5% caustic soda solution in very small excess only, after which the scrubbed oil was again water-washed until the soap number was below 0.005, and finally brightmanner. The characteristics of the finished oil were as follows:

Gravity -API 27.7 Pour p in F Viscosity, SSU at 100 F 42.0 Cetane N 62 Oxygen factor 338 Saponification No 12.5 Soap No 0.01 Neutralization No 0.27 Cold engine starting temperature F 45 Example II.-A Kettleman Hills (California) crudelight gas oil distillate having-the following characteristics:

was pumped through a heat exchanger and a heated to 300 F., then transferred to the vessel or still referred to, equipped with a porous plate partition near the bottom. A concentrated solution of calcium naphthenate in the same distillate was added in an amount such that the final proportion of the salt was 0.5% by weight. "Seed stock (previously air-blown Kettleman distillate) was added to the extent of 2% by.

volume of the charge.

ened.

'The characteristics of the 011 thus prepared were as follows:

Gravity API- 34.7

Pour point F 45 Viscosity, SSU at 100 F 34.6 Cetane No '75 Oxygen factor 432 Soap No a 0.001 Saponification No 12.6 Neutralization No "1---..- 0,2

Cold engine starting temperature F 36 Example III.A clean Kettleman Hills (California) medium gas oil distillate having the following characteristics:

Gravity .I API-- was blended with the finished oil prepared as described in Example II, the proportions of the blend being 86 volume per cent of the clean Kettleman Hills medium distillate and 14 volume per cent of the 75 octane number 011 prepared in accordance with Example II. The characteristics of the blended oil were as follows:

Gravity API.. 34.1 Pour poin F-.. 0 Viscosity, SSU at 100 F 38.5 Cetane No 61 Oxygen factor 62 Cold engine starting temperature F 46 Definitio'ns. -For the purposes of this invention, the following characteristics have the following meanings or' derivations:

The octane number determinations given herein are determined by a procedure known as the Standard Oil Company of California delay meth- 'od, employing a Fairbanks Morse Diesel engine,

in which the ignition delay with combustion occurring at top dead center is utilized as the test criterion and in which the operating variable is the injection advance, equivalent to the ignition delay when firing is made to occur at top dead center. In brief, this procedure is characterized as follows: The fuel to be tested is introduced into the engine and the injection is then advanced or retarded until firing occurs at top center; the ignition delay is read and recorded. The

alphamethylnaphthalene blends which produce greater and lesser ignition delays than the fuel under test. A plot is made of the ignition delays of the octane-alphamethylnaphthalene blends in terms of the percentage of octane in the blends. The ignition delay of the fuel-under test is placed on this plot and its corresponding cetane number is determined. The method may be employed on service engines capable of suflicient control of all operating variables, other than Fairbanks Morse; as described, the method yields results which correlate well with service performance.

The cold engine starting temperatures given herein are determined by a procedureknown as the Standard Oil Company of California cold starting method, in which the lowest ambient temperature at which the engine will start in .iust seconds is measured under service conditions. In brief, this procedure is characterized as follows: The fuel to be tested is introduced into the fuel system of a single cylinder, 1400 R. P. M. precombustion chamber, 4 /2" X 5 /12 bore and stock, 16 to l compression ratio, full scale Caterpillar Diesel engine with injection advance set at -23 BTC and an injection pressure of 1500 lbs/sq. in.; suitable refrigerating equipment is provided to cool the intake air and cylinder jacket to the required low temperatures. Jacket and intake air temperatures are established with the engine stopped, and the engine is then cranked at 280 R. P. M. (the normal cranking speed for this engine) until firing occurs; the time interval between first injection of the fuel and the first firing explosion is measured and recorded as the cranking time. The procedure is repeated with the jacket and intake air temperature either raised or lowered as required to result in starting with just 5'seconds of cranking. This final temperature, an ambient starting temperature of the fuel, is that referred to as cold engine starting temperature; this temperature may be correlated with the cetane number of the fuel. These determinations are representative of field performance.

For the purposes of this invention, the oxygen factor of an oil is determined as follows: A 2 to ml. sample of the oil, at approximately 68 F., is accurately pipetted into a 250 ml. glass-stoppered flask. ml. of a mixture consisting of 60 volumes per cent of C. P. glacial acetic acid and volume per. cent of chloroform are added to the oil, followed by 2.0 ml. of a saturated aqueous solution of potassium iodide. The mixture is shaken vigorously for three minutes and then diluted with about 50 ml. of distilled water. The liberated iodine is titrated with 0.1 normal standardized sodium thiosulfate solution, adding starch indicator just before the end point is reached. Considerable shaking is necessary near the end of the titration. Oxygen factor=(titer in ml. normality of thiosulfate 1120)/(volume of sample in ml.).

For the purposes of the invention, the soap number of an oil is determined as follows: A 5 to 100 ml.-sample of the oil is pipetted into a 250 ml. Squibb funnel, and 10 m1. of saturated aqueous sodium chloride solution, approximately 3 grams of solid sodium chloride and 2 drops of methyl orange indicator are added. The mixture is titrated with standardized dilute hydrochloric acid solution (1 ml. equivalent to 1.0 mg. of KOH) until a pink color persists in the. aqueous layer after 30 seconds of vigorous shaking and \ethyl ether in place of alcohol.

then settling: A light neutral petroleum thinner may be added to hasten settling, if necessary. A blank titration is made, omitting the oil sample, and the titer subtracted from the titer obtained with the oil, to obtain the corrected titer. Soap number= corrected titerxconcentration of HCl in equivalent mg. of KOH per ml.) /(weight of oil sample), the weight of oil sample being derived from volume and specific gravity of the oil tested.

Saponification numbers are determined in accordance with A. S. T. M. D94-38T, Method A. Neutralization numbers are determined in accordance with A. S. T. M. Dl88 27T,. Method B, modified by titration at roomtemperature, by the use of alcoholic hydroxide and by the use of v U. 0. P. characterization factors are discussed in Watson, Nelson and Murphy, Industrial and Engineering Chemistry, volume 27, pages 1460-1464 1935).

The paragraphs below discuss the critical nature of several of .the variables which operate to provide the maximum benefits in the practice of the invention.

The precise character of the oil contemplated for use has been found to be of considerable consequence in providing a set of hydrocarbons ca.- pable of attaining high oxygen factors upon being subjected to the action of oxygen or an oxygen-containing gas such as air, under the circumstances disclosed for the practice of the invention. In general, the factors which have been found of greatest significance in this choice or preliminary preparation of an oil are: relative freedom from large proportions of'aromatic ring structures among the hydrocarbons themselves; relative freedom from asphaltic or resinous materials; and relative volatility of the set of hydrocarbons as a whole.

Oils containing high proportions of aromatic rings are less easily capable of attaining high oxygen factors than are oils of high paraffinicity, although the treatment of oils of high I aromatic content with relatively strong sulfuric ma erna acid or an equivalent chemical reagent or their extraction with liquid solvents such as liquid sulfur dioxide, phenol, aniline, furfural, nitrobenzene and the like, in removing aromatic components or reducing their concentration, sufiices to improve their amenability to treatment in accordance with the invention. These eflects are illustrated in Table I.

Table I Maxi- 01'1 Pretreatment 3 123 factor sew-m F. Kettleman None 123 gas oil. r 360?;720? F. Midway gas do e 01 360 l720 '1. Midway gas 0.5 lb. 98% Hz l/gfll 266 01 3603-72091. Midway gas 2.0 lbs. 98% HzS04/g8l 450 or 3602-720 F. Midway gas Extraction with 100% 80:. 272

The Kettleman gas oil referred to in Table I was a clean distillate, containing substantially no asphaltic or resinous matter; it is understood to contain some 7-16% of aromatic rings and some -70% of paraflins, including side chains. The Midway gas oil referred to was likewise a clean distillate, understood to contain some 15-23% of aromatic rings and some 50% of parafilns, in-

cluding side chains. The preliminary treatments carried out on the Midway as oil as above illustrated increase the parafilnicity of the oil as a whole, to varying degrees. and make the desired type of oxidation more readily possible.

Further. the presence of small amounts of resinous or asphaltic substances appears to prevent the attainment of high oxygen factors in the oils, and the removal of such substances, which may be present by reason of spray or mist entrainment in the original fractionation of the oil, may be effected by a subsequent re-fractionation to eliminate heavy ends, by treatment with clay or analogous adsorbent agents, or by sulfuric acid or solvent extracting treatments.

These efi'ects are illustrated in Table II.

Table II Maxi- Oil Pretreatment f g factor 1 38051-720" F. Kettleman gas None 2 38051720 F. Kettleman gas 0151b. 98% H:SO4/gal 378 3 380-720 F. Kettleman gas 2.0 lbs. 08% Basil/gal... 520 4 tam-120 F. Kettleman gas Extraction with 100% so,. 342 s 38(:-:720 F. Kettleman gas r i tion thru mum cos 6 49%;:380" F. Keitleman gas (Re-iractionation)... 148

The Kettleman gas oil referred to in Table II was the overhead from an imperfect fractionating column and contained small amounts of asphaltic or resinous matter introduced by spray entrainment, as was evidenced by the color of the distillate itself: Refractionation of the distillate or treatment with claywere each suiilcient to remove this material and allow the desirable reactions to progress. As in the case of the Midway distillate referred to in Table I, reagent or solvent treatment effected marked improvement even in the relatively highly parafiinic 380-720 F. Kettleman distillate referred to in Table II, since the quantities of such agents as are there exemplified do more than remove merely asphaltic substances and go far toward aromatic ring removal.

Finally, the boiling point range or relative volatility of the oils affects their relative oxidizability to produce the types of compounds whose presence is measured in terms of oxygen factor and found desirable for the purposes of the invention. Thus the oils capable of attaining highest oxygen factors are those of ordinary kerosene boiling point range of average volatility, and maximum attainable oxygen factor de- The 011 stocks referred to in Table III were all able under these conditions.

asoasao clean distillates from the same crude Kettleman Hills, California, source. In general, as average volatility decreases, preliminary treatment with acid, clay or a selective solvent or analogous treating agent is more effective to increase the maximum attainable oxygen factor than it is to increase the maximum oxygen factor attainable on relatively volatile oils.

The oil stocks exemplified in Tables I, II and III, above were treated with air at 300 F. under similar conditions: 8 volumes air per minute per volume oil; 1.0% calcium naphthenate and 2.5% of "seed stock" as accelerators, and the operations were continued for a sufficient time to reach the maximum oxygen factors attain- Sulfuric acid of higher or lower strength, for example 93% H2804 to 20% a, in variable amounts, and solvents similar in their action to liquid 80:, likewise in higher or lower amounts than those shown, are suitable for use in the pre-treatments described, when such treatment is indicated as desirable for the removal of the originally con tained deleterious hydrocarbon components. Similar relations between oxidizability of the desired type and relative freedom from aromatic rings, asphaltic or resinous matter, and average volatility may be ascertained for operations on oil stocks of different origin than those particularly exemplified above.

Residual petroleum stocks cannot be employe as initial materials in the processes of the invention unless they have been preliminarily subjected to a refining treatment equivalent to an overhead vaporization, for the substantially complete removal of the high boiling asphaltic, resinous and highly reactive hydrocarbons ordinarily contained in petroleum residua. In general, it may be said that when the processes are to be carried out on sets of hydrocarbons of petroleum origin and of the usual straight run or cracked distillate types, relatively free of as- 1 phaltic and resinous material, U. 0. P. characterization factors should be 11.15 or above; if the U. 0. P. characterization factor of such a set of hydrocarbons, prepared in any usual manner from a petroleum source material, is below 11.15, a preliminary treatment of the nature of those indicated will be found necessary. Ori inal or treated distillates of 11.30 or higher U. 0. P. characterization factors may be employed to greater advantage in the oxidizing steps than those with lower factors, andthe highest benefits of the process may be obtained from stocks with factors of 11.50 .and higher. From this it will be seen that the oxidizing processes' of the invention are not ordinarily to be used, in the absence of preliminary treatment, on petroleum stocks which are themselves unusable as Diesel engine fuels: on the contrary, insofar as ordinary petroleum fractions are concerned, the

processes of the invention contemplate an improvement in stocks already of recognized utility as mediumor high-speed compression ignition engine fuels.

In still further illustration of the wide variety of hydrocarbon stocks which may be beneficially treated in accordance with the invention:

A side out gas oil stream from a thermal cracking unit, of light Diesel oil volatility, had a delay method cetane numberof 31 and a U. 0. P characterization factor of 11.12; upon extraction with 200% of liquid 80:, the raflinate had a cetane number of 54 and a U. 0. P. characterization factor of 11.74. This raflinate was blown for 1% hours with 4 volumes of air per minute per volume of oil, at 300 F., in the presence of 1% of calcium naphthenate, and the treated oil washed with water and dilute caustic soda solution in the manner described. The finished treated oil had an oxygen factor of 280 and a delay method octane number of 80.

In the oxidizing step in the process of the invention, temperatures between 200 and 400 F. may be employed, but operations between 250 and 350 F. are more suitable; the preferred range is between 275 and 325 F, and 290-310F. is optimum, almost irrespective of charging stock and of the character of the preliminary treatment. At temperatures below 275 F., the reactions which progress are of highly. beneficial character and products of high oxygen factor are obtained; the rate of reaction, however, is considerably lowerthan it is within the preferred range. Temperatures above about 310 F, are usually avoided as the temperature coefficient for the rate of secondary and deleterious reactions, in which the substances giving rise to high oxygen factors are destroyed, is greater than the temperature coefiicient for the rate of formation of theseprimary and desirable substances. The table below will illustrate the effect of temperature on the results obtained in treating the Kettleman gas oil referred to in Table II, above, preliminarily prepared with a 0.5 lb. 98% HzSOr/gal. treatment, at an air rate of 4 volumes air per minute per volume oil, in' the presence of 1.0% calcium naphthenate and 2.5% of seed stock as catalysts and accelerators, with air passage through a porous plate infinely dispersed condition.

It will be observed that the oxygen factor reaches a maximum and thereafter decreases rapidly,

whatever the temperature of treatment. It is accordingly desirable to continue the treatment with air or an oxygen-carrying gas, at a high temperature, for a time not materially longer'than is suilicient to give an oil of the maximum oxygen factor attainable under the circumstances of the treatment. It will likewise be observed that secondary or side-reaction products increase rapidly as this maximum oxygen factor is approached Y and passed; some of these acidic side-reaction products are undesirable and must be removed from the oil, for the purposes of the invention, and the continuation of the treatment is accordingly undesirable for this reason as well. It is obvious that the treatment with air or an oxygencontaining gas may be terminated at any suitable Generally. the maximum oxygen factor attainable in an oil, when subjected to the conditions here described, will be reached and passed before the neutralization number of the oil reaches 15; it may therefore be said that ordinarily the processes of the invention do not contemplate the continuance of exposure of an oil to an oxygencarrying gas, under reactive conditions, beyond a neutralization number rise of 15 and generally not beyond a neutralization number rise of 12; indeed, a rise in neutrahzation number beyond 10 and sometimes beyond 8 will often indicate that the maximum oxygen factor has been passed, to the detriment of the invention in its best aspects. In actual operations, the course of the reaction may best be observed by the periodic removal of small samples of the oil undergoing oxidation and by carrying out rapid oxygen factor determinations thereon.

Moreover, the oil should not be allowed to remain at or appreciably near an oxidizing temperature for any considerable period of time, subsequent to the attainment of the desired oxygen factor and. particularly, such holding at areactlve temperature should not be allowed in the absence of free oxygen passage. For example, if an oil of desirable and high oxygen factor is held, after air-blowing, at a temperature-such -as 300 F. in the absence of continuing air passage, the oxygen factor decreases rapidly and, in a period as long as two hours, approaches zero. Thiscis to say that the secondary reactions, to which reference has been made, continue at the expense of the primary and desirable products: the value of the oil is accordingly much impaired for the purposes of the invention. It is thus'important to cool the oil to a temperature below that at which this reaction is rapid, namely, to a temperature below 250 F. and preferably as low as F., promptly after the desired oxygen factor has been reached.

During the air or oxygen treatment itself, the maximum oxygen factor attainable in an oil increases with air rate, other conditions remaining constant, up to the point at which bubble size increases excessively. Likewise, when the air rate (expressed in volume of air per minute per tact between liquid oil and oxygen-containing gas is, as described, a vertical cylindrical vessel or still equipped with Filtros or similar porous plate partitions near the bottom, up through which the gas may bedisseminated in small bubbles. The porosity of the plates should be high for maximum gas utilization, and beneficial results will be obtained with decreasing pore size, down to the point at which excessive pressure drop occurs through the plates. In this type of apparatus, a liquid column of quiescent oil 4 feet in height, above the plates, and an air rate of two volumes air per minute per volume of oil has been found satisfactory; such height and air rate are dependent, however, upon pore size and upon the extent to which the oxygen factor of the oil is desired to be carried, in the manner referred to above. In the construction of this and the condensing and water-trapping apparatus,

time prior to the attainment/of the maximum omen factor, with highly desirable results.

such metals as copper, brass, bronze and lead should be avoided; chrome-nickel steel is satisfactory, as is glass-lined material. In the desired rapid cooling of the oil, subsequent to the reaction, the gas should be allowed to continue its passage through the oil until cooling is actually effected, lest the formation of secondary reaction products deplete unnecessarily th quantity of desirable primary products present.

In one mode of operation, the invention may be carried out as exemplified in the flow diagram of the appended figure.

In the figure, I represents a feed tank from which initial hydrocarbons, adapted for the preparation of the improved injection engine fuels of the invention, are fed to the treating system. The initial oils pass through the line 2, controlled by the valve 3, through the pump 4 and line 5 into and through the heat exchanger 8 and line I to a treating vessel 8. In Passing through the heat exchanger 6, the oil is raised to an appropriate temperature by the passage of steam or another heating fluid through lines 8 and Ill. The vessel 8 is equipped with a porous plate ll, of suitable characteristics as described.

' Air or an appropriate oxygen-containing gas is forced by the compressor l2, taking suction through the line l3, through line It into air storage vessel l5 and thence through lines It and I1, the latter controlled at valve l8, into vessel 8 below the porous plate H; the line It carries a pressure control and release valve iii. In the vessel 8, controlled aeration of the oil takes place as described; oxygen-denuded air or other gas, carrying some water, volatile hydrocarbons and such partial oxidation products as are volatile under the conditions of the treatment, leave the vessel through the line 20, pass through the condenser 2l, cooled by water entering at 22 and leaving at 23 by control of the valve 24 in appropriate quantities. Condensed water, hydrocarbons'and partial oxidation products volatile under the circumstances of the treatment in the vessel 8 enter the collecting drum 28. where stratiflcation takes place; water is withdrawn through the line 26, controlled by the valve 21; hydrocarbons and contained oil-soluble materials are returned to the vessel 8 through the line 28 by control of the valve 28; uncondenslble gases leave the system through the line 30, controlled by the valve 3!. In the initiation of the reaction and in order that proper oil temperature may be maintained in the vessel 8, circulation of liquid oil may be maintained through the line 32, controlled by the valves 33 and, into the line 2 and through pump 4, line 5 and heater 8 and returned to the vessel 8 through the line 1 under control of the valve 35: such circulation may take place during the progress of the treatment itself, if desired, and oily condensate may appropriately be passed'into such circulatory system through lines 28 and 38 into line 32, valve 28 being closed and valve 31 open. When the oil in vessel 8 has been treated to the degree desired, as measured by the oxygen factor and neutralization number of samples withdrawn at suitbelow which deleterious side-reactions no longer take place. The treating system is emptied through lines 32, 2, 5 and 40, valves 33 and II being open and valve 35 closed; oil which has found its way below the porous plate ii in the treater 8 may be removed through line 42 controlled by valve 43, thus finding its way into line 32. The oil in line All is passed to agitator 44, where it is washed with water brought in through line 45 and valve 46, and with dilute aqueous alkaline hydroxide solution brought in through the line 41 and valve 48; in the agitator 44, the

8 aqueous washing materials are provided contact are withdrawn through line 49 and valve 50. The

able intervals, the heat exchanger 8 is converted to a cooler by ceasing the passage of steam therethrough through the lines 8 and I 0 and the passage of water through the lines 38 and 38; the oil from the treating vessel is cooled by circulation through line 32, controlled by valves 33 and 3!, into line 2 and through pump 4, line 5 and the cooler 8, through line 1, controlled by valve 35, into the vessel 8; during such cooling of the treated oil, the entry of air to the vessel 8, through the porous plate II, is continued until the body of oil has reached a temperature finished oils of the invention are withdrawn from the agitator 44 through line 5|, controlled by the valve 52, by the pump assembly 53 and passed by line 54 to the storage tank 55. Such a system may be operated batch or continuously, with appropriate controls, as desired.

Moreover, it is important that substantially all strongly acidic substances and salts or soaps of organic acids be removed from the treated oil prior to its employment as a fuel in Diesel engines or prior to its blending with unoxidized distillates, both to assure the stability of the flnished oil and to prevent gumming and fouling of the injection nozzles and combustion chambers of the motors and, in addition, to finally stop all reactions of a secondary nature. This removal may be accomplished as exemplified above, in Examples I and II, by washing with a, dilute alkali metal hydroxide solution and then with water; In removing acidic bodies subsequent to cooling after the primary oxidation step, there should be used no more than a slight excess of alkali metal hydroxide solution, and thealkaline solution is itself preferably dilute. A 2 to 10 B. caustic soda solution has been found suitable. When using 7 B. caustic soda solution, if as much as 4 times the necessary alkaline solution is employed, on the basis of the acid or neutralization number as determined, the oxygen factor of the oil will be found to be lowered remarkably,.for example by as much as 1'70 in a high oxygen factor product; if only 10% excess caustic soda is used in acid removal, the oxygen factor may be lowered by 7-23%. In general, considerable care is justified in this step of the process, in order that oils of high oxygen factor may be retained in stable, effective form for the purposes of the invention.

As oxidation catalysts in the oxygen-reactive stages in the .process of the invention, oil-soluble calcium and sodium salts are preferred, and these or equivalent alkali or alkaline earth salts of naphthenic acids, either natural or synthetic, are eminently suitable. These catalysts are most useful in proportions of about 0.25-l.0% by weight of the oil undergoing oxidation, but

slightly lower and somewhat higher concentrations may be employed if desirable, for example, amounts between 0.10% and 2.5% by weight. In some cases, notably those in which clean, relatively low boiling point stocks are treated, for example a refined kerosene or lamp oil, no catalyst is required to cause the attainment of high oxygen factors. The calcium and sodium salts of the organic acids formed in the course of the oxidizing reaction itself, recoverable in the caustic soda washing step which follows the cooling-of the treated oil, are themselves effective as catalysts in the oxidizing stage of the resinous reaction products at the expense of substances measurable in terms. of oxygen factor, and the quantity of catalyst should accordingly be held as low-as is consistent with the oxygen factor desired to be attained. In addition, a small amount of an oxidized oil, prepared in a previous operation, taken prior or preferably subsequent to washing and neutralizing, will act to accelerate oxidation of the character here desired; the utility of such material is referred to herein under the designation seed stock.

This seed stock, while not essential, has been no value, as their presence leads to the formation of acidic bodies at a rate higher than can be tolerated in the necessary segregation of substances of high oxygen factor; it accordingly appears that different oxidation mechanisms may-predominate when the heavy metal type catalysts are employed.

Subsequent to the removal of relatively strongly acidic reaction products, the partially oxidized oils themselves may be used as injection engine fuels, but in many cases it will be found advanta eous for economic or other reasons to blend such oils with unoxidized oils to produce fuels of certain desired characteristics: see Example III above. In order to bring the proportion of the partially oxidized oil component in such blends to a minimum and to avoid a preliminary treatment .prior to the oxidizing process, a paraflinic distillate of kerosene or more volatile characteristics may suitably be used as charging stock: see Table III and Example III above. In these blending operations, whether the partially oxidizing component is relatively more or less or equally volatile, the desired viscosity, gravity, boiling range and ignition quality may be. realized by suitable choice of initial materials. It is advantageous, for

example, to partially oxidize a high .pour point paraflinic distillate, containing or preliminarily treated to contain but few aromatic rings, and to blend such an oil, properly washed to low acid and soap numbers, with a low pour point, less paraifinic stock of the same boiling range.

For the best preservation of the benefits of the invention, the stock to be blended with the partially oxidized oil should be clean and relatively free from asphaltic and resinous bodies, especially if the stock is of low parafi nicity, as small amounts of such reactive materials destroy the substances measurable in terms of oxygen factor. Generally, clean petroleum distillates of 11.15 and higher U. 0. P. characterization factor should be used in blending, but in many cases improved stability in storage will be obtained by subjecting the unoxidized component. of the blend to a light acid, clay or solvent refining treatment, in the manner disclosed in connection with the preparation ofthe partially oxidized component.

From to 35% of the partially oxidized component will generally be a sufficient proportion in The common physical properties of such blends,

. parative or control purposes.

as the gravity, flash point and the like, may be predicted from the properties of the individual components, but the cetane numbers will be found to be higher than the. values predicted in the usual manner, especially for blends in which the pro- In this specification, repeated reference is made to cetane numbers and oxygen factors of oils. Close correlations may be worked out between oxygen factor and cetane number rise, for com- For example, the relation Cetane No. rise=1.58 /Oxygen factor of fuel has been found to hold, in general, for the rather parafilnic stock referred to herein as of Kettleman Hills, California origin, whether the whole fuel was treated or, on the other hand, a fraction was treated and the finished treated frac tion was blended with an untreated but clean fraction of the same or of different boiling range. The above relation may be modified somewhat with stocks of different origin, and such modifications may be worked out as desired.

The Diesel fuels prepared in the manner described are substantially stable in storage in ordinary fuel containers under all ordinary circumin general no greater than from the base stocks employed in their preparation, and in many cases less.

As used in this specification and in the appended claims, the term injection engine fuel refers to distillate fractions only, but it includes hydrocarbon distillate fractions of kerosene or illuminating oil boiling range and fractions of such fractions, as well as the somewhat less volatile distillates in more usual present use in internal combustion engines of the mediumand high-speed Diesel type; the term accordingly includes hydrocarbon fractions whose A. S. T. M. 50% boiling points at atmospheric pressure are within the range 325 F. to 650 F. As thus used herein, this term includes fractions of relatively narrow boiling point range (so-called short cuts or heart cuts) as well as fractions of wider boiling point range (so-called long cuts).

While various'specific embodiments of the invention have been illustrated and described above it is obvious that many modifications and adaptations may be made without departing there from, and all such changes as are included within the scope of the appended claims are embraced thereby. v i i We 'claim:

1. A process of preparing an improved injecfree from asphalticand resinous materials and from large proportions of aromatic ring compounds to treatment in liquid phase with an oxygen-containing gas at a temperature within the range 200 to 400 F. for a period of time sufficient to produce an oil having an oxygen factor of higher than about 5 but insufficient to increase the neutralization number of the oil by more than about 15, arresting the said treatment before the oxygen factor of the produced oil decreases to below about 5, and removing directly measurable in terms of oxygen factor of I the said fuel, comprising subjecting a petroleum distillate injection engine fuel relatively free from asphaltic and resinous materials and from large proportions of aromatic ring compounds, having an A. S. T. M. 50% boiling point within the range 325 to 650 F. and a U. 0. P. characterization factor above about 11.15 to treatment in liquid phase with an oxygen-containing gas at a temperature within the range 200 to 400 F. for a period of time sufflcient to produce an oil having an oxygen factor of higher than about 5 but insufficient to increase the neutralization number of the oil by more than about 15, arresting the said treatment before the oxygen factor of the produced oil decreases to below about 5, removing acidic reaction. products and washing the substantially acid-free oil with water without reducing the oxygen factor thereof to below about 5.

3. A process of preparing an improved injection engine fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate injection engine fuel relatively free from asphaltic and resinous materials and from large proportions of aromatic ring compounds, having an A. S. T. M. 50% boiling point within the range 325 to 650 F. and all. 0. P. characterization factor above about 11.15 to treatment in liquid phase with an oxygen-containing gas at a temperature within the range 200 to 400 F. for a period of time sufficient to produce an oil having an oxygen factor of higher than about 5 but insufficient to increase the neutralization number of the oil by more than about 15, arresting the said treatment before the oxygen factor of the produced 011 decreases to below about 5, and removing acidic reaction products from the produced oil without reducing the oxygen factor thereof to below about 5.

4. A process of preparing an improved injection engine fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate injection engine fuel relatively free from asphaltic and resinous materials and from large proportions of aromatic ring compounds, having an A. S. T. M. 50% boiling point within the range 325 to 650 F. and a U. 0. P. characterization factor above about 11.15 to treatment in liquid phase with an oxygen-containing gas at a temperature within the range 200 to 400 F in the presence of an oil-soluble oxidation catalyst for a period of time sufficient to produce an oil having an oxygen factor of higher than about 50, arresting the said treatment before the oxygen factor of the produced oil decreases to below about 50, and substantially completely remov- I tion engine fuel containing substantial proporfrom the produced 011 without reducing the oxygen factor thereof to below about 35.

5. A process of preparing an improved injection enginefuel containing substantial proportions of chemically combined reactive oxygen. which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate injection engine fuel relatively free from asphaltic and resinous materials and from large proportions of aromatic ring compounds, having an A. S. T. M. 50% boiling point within the range 325 to 650 F. and a U. 0. P. characterization factor above about 11.15 to treatment in liquid phase with an oxygen-containing gas at a temperature within the range 200 to 400 F. in the presence of an oil-soluble oxidation catalyst for a period of time suilicient to produce an oil having an oxygen factor of higher than about 50, arresting the said treatment before the oxygen factor of the produced oil decreases to below about 50, and reducing the soap number and the neutralization number of the produced oil to below 0.05 and 0.25, respectively, by washing with dilute aqueous alkaline solution and with water, in the order named, without reducing the oxygen factor of the produced oil to below about 35.

o. A process of preparing an improved injection engine fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor oithe said fuel. comprising. subjecting a petroleum distillate injection engine fuel relatively free from asphaltic and resinous materials and from large proportions of aromatic ring compounds, having an A. S. T. M. 50% boiling point within the range 325 to 650 F. and a U. 0. P. characterlzation factor above about 11.15 to treatmentinliquid phase with an oxygen-containing gas at a temperature within the range 250 to 400 F. in the presence of an oil-soluble oxidation catalyst for a period of time sufficient to produce an oil having an oxygen factor of higher than about 50, arresting the said treatment before the oxy en factor of the produced oil decreases to below about 50, substantially completely removing soaps and corrosive acidic reaction products without reducing the oxygen factor of the produced oil to below about 35, and blending the said substantially soap-free and acid-free oil with from V5 to 20 times its volume of a clean petroleum hydrocarbon distillate of injection engine fuel characteristics.

l. A process of preparing an improved injections of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate relatively free from asphaltic and reslnous materials and from large proportions of aromatic ring compounds, having an A. S. T. M. 50% boiling point within the range 325 to 550 F. and a U. 0. P. characterization factor above about 11.3 to treatment in liquid phase with an oxygen-containing gas at a temperature within the range 250 to 350F. for a period of time suiiicient to produce an oil having an oxygen factor of higher than about 250 but insufficient to increase the neutralization number of the oil by more than about 15, cooling the treated oil to a temperature below about 250 F., and reing soaps and corrosive acidic reaction products 7 moving corrosive acidic reaction products without reducing the oxygen factor of the substantially acid-free oil to below about 175.

8. A process of preparing an improved injection engine fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate relatively free from asphaltic and resinous materials and from large proportions of aromatic ring compounds, having an A. S. T. M. 50% boiling point within the range 325 to 500 F. and a U. 0. P. characterization factor above about 11.4 to treatment in liquid phase with an oxygen-containing gas at a temperature within the range 250 to 350 F. for a period of time sufficient to produce an oil having an oxygen factor of higher than about'400 but insufficient to increase the neutralization number of the oil by more than about 15, cooling the treated oil to a temperature below about 250 F., and removing corrosive acidic reaction products without reducing the oxygen factor of the substantially acid-free oil to below about 280.

9. A process of preparing an improved injection engine fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate relatively free from asphaltic and resinous materials and from large proportions aromatic ring compounds, having an A. S. T. M. 50% boiling point within the range 550 to 650 F. and a U. 0. P. characterization factor above about 11.5 to treatment in liquid phase-with an oxygen-containing gas at a temperature within the range 250 to 350 F. for a period of time suificient to produce an oil having an oxygen factor of higher than about 50, cooling the treated oil to a temperature below about 250 F., removing corrosive acidic reaction products and washing the treated oil with water without reducing the oxygen factor of the substantially acid-free oil to below about 35.

12. A process of preparing an improved injection engine fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate relatively free from asphaltic and resinous materials and from large proportions of aromatic ring compounds, having an A. S. T. M. 50% boiling point within the range 325 to 650 F. and a U. 0. P. characterization factor above about 11.15 to treatment in liquid phase with I an oxygen-containing gas at a temperature within of aromatic ring compoundshavingan A. S. T. M. 50% boiling point within the range 325? to 475 F. and a U. 0. P. characterization factor above about 11.5 to treatment in liquid phase with an oxygen-containing gas at a temperature within the range 250 to 350 F. for a period of time sufficient to produce an oil having an oxygen factor of higher than about 550 but insufficient to increase the neutralization number of the oil by morethan about 15, cooling the treated oil to a temperature below about 250 F..

and removing corrosive acidic reaction prod- 'ucts without reducing the oxygen factor 'of the substantially acid-free oil to below about 385.

10. A process of preparing an improved injection engine fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate relatively free from asphaltic and resinous materials and from large proportions of aromatic ring compounds, having an A. S. T. M. 50% boiling point within the range 450 to 550 F. and'a U. 0. P. characterization factor above about 11.3 to treatment in liquid phase with an oxygen-containing gas at a temperature within the range 250 to 350 F. for a period of time suificient to produce an oil having an oxygen factor of higher than about 50, cooling the treated oil to a temperature below about 250 F., removing corrosive acidic reaction products and washing the treated oil with water without re- .ducing the oxygen factor of the substantially acid-free oil to below about 35.

11. A process of preparing an improved injection engine fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate relatively free from asphaltic and resinous materials and from large proportions of the range 275 to 325 F. for a period of time suflicie'nt to produce an oil having an oxygen factor of higher than about 50 but insuificient to increase the neutralization number of the oil by more than about 15, cooling the treated oil to a temperature below about 250 F. while continuing the treatment with the oxygen-containing gas, and reducing the soap number and the neutralization number of the treated oil to below 0.05 and 0.25, respectively, without reducing the oxygen factor of the produced substantially soap-freeand acid-free oil to below about 35.

13. A process of preparing an improved injection engine fuel containing substantial proportions of chemically combined reactive oxygen,

which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate relatively free from asphaltic and resinous materials and from large proportions of aromatic ring compounds, having an A. S. T. M. 50% boiling point within the range 325 to 650 F. and a U. 0. P. characterization factor above about 11.15 to treatment in liquid phase with an oxygen-containing gas at a temperature within I the range 290 to 310 F. for a period of time sufficient to produce an oil having an oxygen factor of higher than about 50 but insuflicient to increase the neutralization number of the oil by more than about 15, cooling the treated oil to a temperature below about 250 F. while continuing the treatment with the oxygen-containing gas, and reducing the soap number and the neutralization number of the treated oil to below 0.05 and 0.25, respectively, without reducing the oxygen factor of the produced substantially soapfree and acid-free oil to below about 35.

14. A process of preparing an iriproved injection engine fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate relatively free from asphaltic and resinous materials and from large proportions of oxygen-containing gas at a temperature within the range 250 to 350 F., in the presence of a catalyst selected from the group consisting of alkali and alkaline earth metal oil-soluble soaps, for a period of time suflicient to produce an oil having an oxygen factor of higher than about 50 but insuificient to increase the neutralization number of the oil by more than about 15, cooling the treated oil to a temperature below about 250 F. while continuing the treatment with the oxygen-containing gas, and reducing the soap number and the neutralization number of the treated oil to below 0.05 and 0.25, respectively, without reducing the oxygen factor of the produced substantially soap-free and acid-free oil to below about 35.

15. A process of preparing an improved injection engine fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising subjecting a petroleum distillate relatively free from asphaltic and resinous materials and from large proportions of aromatic ring compounds, having an A. S. T. M. 50% boiling point within the range 325 to 650 F. and a U. 0. P. characterization factor above about 11.15 to treatment in liquid phase with an oxygen-containing gas at a temperature within the range 250 to 350 F., in the presence of between 0.1% and 2.5% by weight of calcium naphthenate, for a period of time suflicient to produce an oil having an oxygen factor of higher than about 50, cooling the treated oil to a temperature below about 250 F. while continuing the treatment with the oxygen-containing gas, and reducing the soap number and the neutralization number of the treated oil to below 0.02 and 0.25 respectively, without reducing the oxygen factor of the produced substantially soap-free and acidfree oil to below about 35.

l6.' A process of preparing an improved injection engine fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising preliminarily subjecting a crude petroleum distillate to a refining treatment effective to materially reduce the content of components of relatively high carbon to hydrogen ratio, to substantially completely remove asphaltic and resinous material and to produce an oil having a U. 0. P. characterization factor of at least 11.15, and thereafter subjecting the said preliminarily treated distillate to treatment in liquid phase with an oxygen-containing gas at a temperature within the range 200 to 400 F. for a period of time suflicient to produce an oilhaving an oxygen factor of higher than about 5 but insufflcient to increase the neutralization number of the oil by more than about 15, arresting the said treatment before theoxygen factorof the treated oil decreases to below about 5, removing acidic reaction products from the treated oil, and washing with water without reducing the oxygen factor of the treated substantially acid-free oil to below about 5.

1'7. A process of preparing an improved injection engine fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, comprising preliminarily subjecting a crude petroleum distillate to a refinin treatment effective to materially reduce the content of components of relatively high carbon to hydrogen ratio, to substantially completely remove asphaltic and resinous material and to produce an oil having a U. 0. P. characterization factor of at least 11.15, and thereafter subjecting the said preliminarily treated distillate to treatment in liquid phase with an oxygen-containing gas at a temperature within the range 200 to 400 F. for a period of time sufilcient to produce an oil having an oxygen factor of higher than about 50 but insufiicientto increase the neutralization number of the oil by more than about 15, arresting the said treatment before the oxygen factor of the treated oil decreases to below about 50, and removing acidic reaction products from the treated oil without reducing the oxygen factor thereof to below about 35, and blending the said produced substantially acid-free oil with from to 20 times its volume of a clean petroleum distillate of injection engine fuel characteristics.

18. An improved injection engine fuel containing substantial proportions of chemically combined reactive oxygen, which chemically combined reactive oxygen is directly measurable in terms of oxygen factor of the said fuel, having an oxygen factor higher than about 5, a soap number no higher than 0.05 and a neutralization number no higher than about 0.25, prepared by subjecting a petroleum distillate injection engine fuel relatively free from asphaltic and resinous materials and from large proportions of aromatic ring compounds, having an A. S. T. M.

50% boiling point within the range 325 to 650 F. and a U. 0. P. characterization factor above about 11.15 to treatment in liquid phase with an oxygen-containing gas at a temperature within the range 200 to 400 F. for a period of time suflicient to produce an oil having an oxygen factor of higher than 5 but insumcient to increase the neutralization number of the oil by more than about 15, arresting the said treatment before the oxygen factor of the produced oil decreases to below 5, and reducing the soap number and the neutralization number of the produced oil to below 0.05 and 0.25, respectively, without reducing the oxygen factor of the produced oil to below 5.

THOMAS H. SCHULTZ.

IRVING E. LEVINE.

HOMER B. WELLMAN. 

